Plotagraphs are now no longer allowed in r/Cinemagraphs. Plotagraphs that have been submitted after this post goes live can be reported and mods will review and decide if they count as plotagraphs or not.The difference between Plotagraphs and Cinemagraphs are pretty simple:

Plotaraphs start from a static photograph that has no motion

Cinemagraphs start from a video

The final decision of what stays and what goes is at the moderators' discretion. If a mod decides that something that you think is plotograph is sufficiently cinemagraphic enough to stay, that is up to the moderator who makes the call.

I've recently slightly updated the definition of the Cinemagraph. Many people seem to think that artificially stopping some aspect of the picture is necessary - it is not. Here's a link to our definition. Note that I've spoken to or read articles from dozens of Cinemagraph makers, including some people who pioneered this art form, to make this definition.

What is a Cinemagraph anyways?

Cinemagraph Basics

A cinemagraph is a high quality gif. It needs a certain resolution (something like Tumblr's limitation of image widths) and a good colour palette.

A cinemagraph is very smoothly looped. There should not be a noticeable "seam" to a cinemagraph.

The loop creates a certain quality of motion. This is subtle, but important. The quality of the movement is what defines the feel of the cinemagraph. It should be well crafted, smooth, and natural within the boundaries of the universe of the cinemagraph.

A Cinemagraph has an immobile frame of reference. Just like a photograph, the "world" of a cinemagraph doesn't move.

A Cinemagraph is distinct from a Plotagraph. Cinemagraphs typically are sourced from videos and are made by looping existing movement; Plotagraphs are sourced from photos and are made by adding artificial movement.

All definitions include these things; these are the silver (not golden) rules of Cinemagraphy, in that they can clearly help us define what is not a cinemagraph, though they don't really give us a definitive answer about what is a cinemagraph.